How can I store a string of the session.server.landinguri to pass as a variable?

I would like to pass a variable that is part of the session.server.landinguri variable and am having trouble manipulating the URI.

 

Example:

 

https://website.com/saml/idp/profile/directorpost/sso?VariableID=1234567890

 

I need to pass just the VariableID value as a new variable (session.user.VariableID), however I haven't figured out how to strip this from the landinguri. The farthest I've gotten was just simply pass "session.server.landinguri" for the "session.user.VariableID" variable, which is a good start.

 

Thanks in advance for any help with this!